(1) Field of the Invention
This invention relates to a novel trisazo compound, particularly useful as a charge carrier generating material for electrophotographic elements, and a process for manufacturing same.
(2) Description of the Prior Art
It has heretofore been known that trisazo or disazo compounds are effective as a charge carrier generating pigment used in a charge carrier generating layer of a multilayer-type electrophotographic element, one of the elements used in the electrophotographic processes. The multilayer-type electrophotographic element is an element comprising an electrically conductive substrate; a charge carrier generating layer which contains a charge carrier generating pigment capable of generating charge carriers when exposed to light radiation, which layer is formed as a thin film on the substrate by use of an adequate means, for example, vacuum deposition of the pigment, application of the pigment solution, or application of a resin-containing solution having fine particles of the pigment dispersed therein; and a charge transfer layer capable of accepting the charge carriers generated in the charge carrier generating layer and transferring them, which layer is formed on the charge carrier generating layer and usually contains a charge transfer substance and a binder. As disazo or trisazo compounds used in this kind of the electrophotographic element there have been known benzidine type disazo pigments disclosed in Japanese Laid-Open Patent Application Nos. 37543/1972 and 55643/1977, triphenylamine type trisazo pigments (see Japanese Laid-open Patent Application No. 132547/1978 and U.S. Pat. No. 4,279,981) and the like.
However, the multilayer-type electrophotographic elements using conventional disazo or trisazo compounds as charge carriers generating substance are defective in that these elements have a lower sensitivity than those using an inorganic substance such as arsenic selenide (As.sub.2 Se.sub.3) alloy as photosensitive material, and are unsuitable for high speed copying machines. In addition, the demand for elements for use in laser printers, and the development of elements capable of exhibiting high sensitivity especially to the wavelength region of semiconductor lasers has been growing.